The piezoelectric type inkjet head includes many elements that are of the capacitance-type actuators as ink ejecting actuators. Therefore, the high speed piezoelectric type inkjet head requires a driving device that drives the capacitance-type actuators at high speed.
The driving device drives the actuator by passing a forward or reverse current through the actuator. The actuator may be charged by the passage of the reverse current after being charged by the passage of the forward current. Thus, the actuator obtains a degree of vibration corresponding to a voltage level double an output voltage of a DC power supply.
The driving device discharges the voltage at the actuator to near zero within a period between the charging performed by the passage of the forward current and the charging performed by the passage of the reverse current. When the discharge period is inserted between the charging period of the passage of the forward current and the charging period of the passage of the reverse current, power consumption becomes a half compared with the case in which a transition is immediately made to the charging performed by the passage of the reverse current from the charging performed by the passage of the forward current or the case in which the actuator is charged only by the passage of the unidirectional current using a value double the output voltage.
However, power consumption in the case including the discharge period is reduced up to a half of the power consumption in the case not including the discharge period. In order to further reduce the power consumption in the case including the discharge period, it is necessary to increase the number of power supplies to perform the multi-stage discharge. However, in such cases, although the power consumption is reduced, unfortunately a configuration of the driving device becomes complicated.